Axial piston pump or motor arrangement



Dec. 6, 1966 P. BOSCH 3,289,505

AXIAL PISTON PUMP OR MOTOR ARRANGEMENT Filed March 16, 1965 4 Sheets-Sheet l Dec. 6, 1966 P. BOSCH 3,289,606

AXIAL PISTON PUMP OR MOTOR ARRANGEMENT Filed March 16, 1965 4 Sheets-Sheet z.:

/Af VFA/rop Dec. 6, 1966 P. BOSCH 3,289,606

AXIAL PISTON PUMP OR MOTOR ARRANGEMENT Filed MaICh 16, 1965 4 Sheets-Sheet 5 Dec. 6, 1966 P. BOSCH 3,289,606

AXIAL PISTON PUMP OR MOTOR ARRANGEMENT Filed MaICh 16, 1965 4 SheebSSheet 4 United States Patent Ollice 3,289,606 Patented Dec. 6, 1966 1s creams. (ci. 10s-rc2) The present invention relates to an taxi-al piston pump or motor arrangement, and more `particularly to an arrangement in which a rotary cylinder block is pressed by hydrostatic forces against a stationary control tace.

It is known to apply hydrostatic forces against the cylinder block of an axial piston pump or motor in order to prevent a separation of the cylinder block from the control face in which inlet and outlet ports are provided, or a tilting of the cylinder block about one edge abutting the control face. A spring is often used for the same purpose, but the spring `force is frequently insufcient since the spring must be of limited size due to the small available space,

In one construction of the prior art, leakage oil is dischanged through an ovenpressure valve, and when the cylinder block rotates, the leakage oil accumulated in the casing is rotated and thrown by the centrifugal force against the casing wall so that iirst the outer part of the casing and then the inner part are filled with oil so that the pressure valve, which is arranged in the longitudinal axis of the apparatus, permits iirst the air to escape `from the casing, and when the same is filled with oil, oil pass-es through the pressure valve. However, a substantial pressure cannot be developed for urging the cylinder block against the control face of the stationary casing, since substantially the same pressure acts on opposite end faces of the cylinder block.

It is one object of the invention to overcome disadvantages of known arrangements for .pressing the cylinder block against a control face of the casing, and to provide an axial piston pump or motor with apparatus producing a lgreater hydrostatic pressure on one side of the cylinder block than on the side sliding on the control face of the casing, so that the oil losses `are a minimum, and efficiency of the pump or :motor is la maximum.

Another object of the invention is to provide an axial .piston hydraulic apparatus, such as a motor or pump, with means producing a small overpressure of the oil in the casing, but a substantial pressure difference between the pressure acting on opposite sides of the cylinder block.

Another object of the invention is to make the hydrostatic pressure by which the cylinder block is pressed against the control face, depending on the rotary speed of the cylinder block so that the hydrostatic balancing pressure increases with the number of rotation of the apparatus, preferably in accordance with the square of the rotary speed.

Another object of the invention is `to make the hydrostatic balancing pressure dependent on the relative position of the cylinder bloc-k land control face in such a manner that the hydrostatic balancing torce incre-ases as a gap between the control face of the casing and the cylinder block increases so that the gaip is again reduced to axial piston pump or motor so that a control face of the cylinder block is pressed against a control face of the casing with such a force that leakage losses are held to a minimum, but smooth sliding engagement between the control faces is assured.

With these obje-cts in view, the present invention relates to an improvement of an axial piston pump or motor which comprises a casing with a first control face having high pressure and low press-nre ports for a fiuid; and ro tary cylinder means having a second control face in slid ing contact with the first control face and ports opening on the second control face Iand connected to cylinders in which pistons are disposed for axial movement.

In one embodiment of the invention, the rst and second control faces form two separate 'recessed areas, one of which communicates, for example through a duct in the casing, with the low pressure side of the pump or motor.

On its side removed from the second control face, the cylinder means has a surface forming a cavity in the casing which communicates with the other recessed area between the control lfaces.

Leakage fluid from the high pressure port Hows between the control faces into the recessed areas and consequently into the cavity in the casing. The fluid under pressure accumulating in the cavity produces on the surface of the cylinder means a pressure exceeding the opposing `pressure acting on lthe second control face only in the region of the recessed area which communicates with the cavity, since the rst mentioned recessed area is connected wit-h the low pressure conduit, and produces no pressure opposing the pressure acting in the cavity of the casing. Since the pressure in the casing exceeds the pressure acting on the control face of the cylinder means, the control face of the cylinder means is pressed against the control tace of the casing, and the leakage losses are held to a minimum.

In the preferred embodiment of the invention, the recessed area which communicates with the Cavity in the casing, is connected by throttling means with the low pressure conduit so that the hydrostatic pressure prevailing in the cavity of the casing and acting o-n the cylinder means, cannot exceed a predetermined limit. The t-hrottling means may be modiiied in accordance with speciiic requirements, such as different rotary speeds and inclinations of the slanted guide surface of the casing by which the sequential axial movements of the pistons are obtained during rotation of the cylinder means with the piston means of the axialpiston pump or motor.

In one embodiment of the invention, one of the recessed areas is circular and disposed concentric with the axis of rotation, while the other recessed area is annular and surrounds the inner recessed area concentric with the same.

In another embodiment of the invention, the inner and outer areas are again concentric, but are eccentric in relation to the rotary cylinder means to compensate certain eccentric forces acting on the cylinder means. Particularly, the negative pressure areas which are connected to the low pressure side of the hydraulic apparatus, can be eccentrically arranged to compensate tilting moments produced by assymmetrical centrifugal forces acting on the cylinder block.

The recessed areas are preferably provided only in the control face of the casing, which is made on a thick control block at one end of the casing. This arrangement has the advantage that the recessed areas can be easily machined into the control block, particularly if the two recessed areas are annular and circular. In accordance with the present invention, the throttling means which limit the pressure in the-cavity,

cartacee d can be constructed in several ways. In one embodiment of the invention, a spring loaded check valve is provided in a duct of the casing, and more particularly of the control block of the casing. In another embodiment of the invention, the throttling means include a valve which is hydraulically shifted for reducing or increasing the open cross section of a throttling duct. In a third embodiment of the invention, the throttling valve is disposed in the rotary cylinder block and has a valve member responsive to the centrifugal force acting thereon during rotation -of the cylinder block to close a duct through which the cavity in the casing can communicate with the low pressure side of the pump or motor. In such an arrangement, the pressure in the cavity rises in accordance with the square of the rotary speed of the cylinder block, and a far greater pressure urges the cylinder block against the control face of the easing when the apparatus operates at high rotary speed.

In some embodiments of the invention, an inner recessed area is connected with the cavity in the casing, and an outer recessed area is directly connected with the low pressure side of the hydraulic apparatus. In another embodiment of the invention, the inner recessed area communicates with a cavity in the casing to provide pressure fluid to the same, while an outer recessed area communicates with the lower pressure side, and also with a throttling duct with a throttling valve communica-ting with the cavity in the casing. In a further embodiment of the invention the inner recessed area communicates with the low pressure side of the apparatus and the outer recessed area communicates directly with the cavity in the casing. Throttling means in the cylinder block preferably including a valve responsive to the centrifugal force, connect the cavity in the casing with the inner recessed area.

The novel features which lare considered as characteristie for the invention are set forth in particular in the appended claims. The invention itself, however, bo-th Ias to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. l is an axial sectional view illustrating one embodiment of the invention;

FIG. 2 is a fragmentary axial sectional view taken on line II-II in FIG. 1;

FIG. 3 is a cross sectional view taken on line Ill-III in FIG. l;

FIG. 4 is a cross sectional view corresponding to FIG. 3 but illustrating a modified embodiment which generally corresponds to the construction illustrated in FIGS. 1 `and 2;

FIG. 5 is a fragmentary axial sectional view of the embodiment of FIG. 4;

FIG. 6 is a fragmentary axial sectional view on a larger scale and illustrating another embodiment of the invention, parts of the apparatus being omitted in FIG. 6 for the sake of simplicity and corresponding to the structure shown in FIGS. 1 and 2;

FIG. 7 is a fragmentary axial `sectional view illustrating moditied parts of another embodiment of the invention which otherwise corresponds to FIG. 1 and FIG. 2;

FIG. 8 is an axial sectional view illustrating another embodiment of the invention; and

FIG. 9 is a fragmentary sectional view taken on line IX-IX in FIG. 8.

Referring now vto the drawings, -and more particularly to FIGS. 1 to 3, a casing means includes a control block 11, and a hollow casing part 12 which is closed by control block 11. A shaft 13 is mounted in a bore 14 of block 11 and in a bore 15 of casing 12, Ia sealing ring 1S preventing the leakage of oil out of the casing. Shaft 13 carries a cylinder 'block 18 which is connected to shaft 13 for rotation therewith by wedge-shaped teeth 17. Cylinder block 18 has seven cylinders 19 in which pistons 20 `are mounted for axial movement. The ends of pistons 20 have sockets receiving spherical elements 21 `which are secured to slide shoes 22 which are guided for sliding movement on a slanted abutment surface of a stationary block 23 forming part of the casing. A ring 24, and a iiange ring 2S hold the slide shoes 22 on the slanted surface of member 23. It will :be understood that rotation of shaft 13 by means of a motor, not shown, will cause rotation of cylinder block 18, and successive axial movements of pistons 2t) as slide shoes 22 move over portions of the `abutment surface which are spaced different distances from cylinder block 1S.

A cylindrical space 26 is provided in cylinder block 18 and receives a coil spring 27 surrounding a portion of shaft 13 and abutting with pretension on a washer supported on the toothed ring 17, and also on the shoulder 27 so that cylinder block 13 is urged by spring 27 to the left as viewed in FIGS. 1 and 2. Cylinder block 18 has a smooth circular control face 18a in sliding contact with a corresponding control face 11a of control block 11.

The section of FIG. 2 shows conduits 28 and 29 opening in elongated part-circular ports 31 land 32 'on control face 11a, as best seen in FIG. 3. Each cylinder 19 has a port 19a opening on control face 18a `in the region of ports 31 and 32, as best seen in FIG. 2, so that during rotation of cylinder iblock 18, the cylinders alternately communicate with cond-nits 28 and 29 through which fluid under high pressure is supplied and fluid under low pressure is discharged. If the apparatus is operated as a motor, the piston 2t) in the position of FIGS. 1 and 2 will draw low pressure -uid through conduit 28, while high pressure fluid supplied through conduit 29 land port 32 into a cylinder 19 will cause the respective piston to move away which is permitted by the slanted abutment face of casing block 23 when the cylinder block 18 turns.

The inner space 26 communicates through a bore surrounding shaft 13 with la recessed annular area in control face 18a surrounding shaft 13. A corresponding annular recessed area 33 is provided in control face 11a and communicates through a duct 341 with `a duct 35 in which `a throttling check valve 36 is mounted in a position closing duct 35 under the action of a spring whose tension is preselected so that a certain predetermined pressure in ducts 35 and 30 and in area 33 is required for opening the check val-ve in which event fluid is discharged through the outlet duct 37 which is connected by conduit means, not shown, to the conduit 2S or 29 through which uid flows at lower pressure depending on whether the apparatus is operated as pump or motor.

As best seen in FIG. 3, segment-shaped surfaces 38, an outer circular surface 39, and an inner circular surface 30 are provided on control face 11a which cooperate with corresponding face portions of control face 18a to axially support the cylinder block 18. Between the segment-shaped surface portions 33, and around the same, recessed areas 40 are provided in control face 11a which are generally annular configuration and surround the inner annular recessed area 33, separated from the same `by the circular surface lportion 3d which is in sliding contact with control face 13a. A duct 41 connects the outer recessed area 40 in control face 11a with the outlet duct 37, passing through a chamber in which the spring of check valve 36 is disposed.

During operation of the hydraulic apparatus as pump or motor in any desired direction of rotation, fluid flows through conduits 28 and 29, and through ports 31 and 32 into ports 19a of cylinders 19 and out of the salme. The fluid owing through ports 31 and 32 leaks across the contact surface 30 and flows partly into the inner recessed area 33, and partly into the outer recessed area di). Fluids in the recessed area 4@ are free to iiow through.

outlet duct 41, 37 to the low pressure conduit of the hydraulic apparatus, and is prevented from flowing into the cavity 45 formed between the surface of the cylinder block 18 and the casing portion 12 since the circular contact face 39 separates the recessed area 40 from the cavity portion which surrounds parts of contact block 11 and the adjacent portions of the cylinder block 18, as best seen in FIG. l.

Pressure fluid flowing from ports 32 into the inner circular recessed area 33` tends to ow through ducts 34 and 35 to the discharge duct 37, but such flow is blocked by check valve 37. Consequently, the pressure increases in recessed area 33, and pressure uid passes through space 26, the toothed ring 17 which has suicient play, and into the cavity 45 so that a pressure is `built up in cavity 45 which corresponds to the pres-sure prevailing in the recessed inner area 33. This pressure acts on the surface of cylinder block 18 to urge the cylinder block to the left as viewed in FIG. 1 so that control face 18a is pressed against control face 11n, This pressure is added to the pressure produced 'by the pretensioned coil spring 27.

The same specific pressure prevails on opposite sides of cylinder block 18, but since the pressure in the large recessed area 4,0 is relieved through discharge duct 41, 36, the pressure acting only in the small recessed area 33 urges cylinder block 18 to the right, while the far greater total transverse surface of cylinder block 18 is exposed to the specific pressure prevailing in cavity 45. Consequently, the hydrostatic pressure urging the cylinder block to the left is far greater than the press-ure exerted on cylinder block 18 in the recessed area 33. By suitably selecting the area 40, and the surface of the segment-shaped contact `faces 38, any desired hydrostatic pressure differential can be produced. Since the surface of segments 38 and of recessed areas 40 is comparatively great, only a small pressure differential is sufficient for producing a su'bstantial hydrostatic balancing force urging cylinder block 18 against control face 11a. Since the pressure in cavity 45 is not particularly high, there are no diculties encountered in sealing casing 12. When the specific pressure in cavity 45 exceeds a predetermined limit, check valve 36 opens, and a throttled flow of pressure fluid takes place thro-ugh conduits 34, 35, 37 to the low pressure side of the apparatus, until the pressure has dropped suciently for check valve 36 to close. Thereupon, the pressure may be built up again in cavity 45 by leakage oil passing from ports 32 or 31 into the inner recessed area 33.

In the embodiment of FIG. 3, the substantially circular and annular recessed areas 33 and 40 are concentric, and also concentric with the axis of shaft 13. In the modified embodiment of FIG. 4 the circular and annular areas 33 and 40 are still concentric with each other, but are arranged eccentric to the axis of rotation of shaft 13. The embodiments of FIGS. 4 and 5 corresponds otherwise to the embodiment of FIGS. 1 to 3, and like parts are indicated by the same reference numerals while modified parts are indicated by primed reference numerals.

The annular and circular contact surface 30 has ports 31 and 32 through which fluid is supplied and discharged as explained with reference to FIGS. 2 and 3. The inner recessed area 33 in control `face 11a communicates through ducts 34, 35, and check valve 36 and discharge to the asymmetric arrangement of the contact faces and recessed areas of the control face 11a, a greater portion of the recessed area 33 is located in the upper half of FIG. 4 than in the lower half, while the recessed area 40" and the contact surfaces 38' have a greater part in the lower portion of FIG. 4 than in the upper portion.

Although the recessed areas are `arranged asymmetrically, they can be inexpensively Imachined on a lathe, since they are bounded by circular lines. The construction may be further simplified Iby making the segmentshaped contact surfaces 38 of the same size.

As described reference to the embodiment of FIGS. l to 3, a pressure difference develops between the recessed area 33 and lthe portion of control face 11 formed by contact surfaces 38 and recessed area 44]', since the recessed areas 40 are connected by duct 4tl to the low pressure conduit of the apparatus, while the check valve 37 causes building up of pressure in the recessed area 33', and consequently in the cavity 45. In the lower half of control face 11a, the conditions are reversed, and a smaller portion of recessed area 33 produces high pressure, while a comparatively larger portion of the low pressure area 40', 38" is connected to the low pressure side of the hydraulic apparatus. In cavity 45, the same pressure develops as in the high pressure area 33', and since the opposing force is smaller in the lower portion of control face 11a than in the upper :portion of the same, a greater force will act to press the lower portion of cylinder block 18 against the lower portion of control face 11a, as indicated by arrow 46 in FIG. 5 than in the upper portion of the cylinder Iblock. In fact, it is possible to produce a counteracting force 44 in the upper portion of the cylinder block which urges the cylinder `block away from control face 11n.

Upon rotation of the cylinder block 18, centrifugal forces indicated by arrows 42 act on pistons 20. Since the piston in the upper parts of the cylinder block are farther spaced `from the contacting control faces than the pistons in the lower part of the cylinder block, the centrifugal forces developed by the upper piston act on a longer lever arm and tend to tilt the cylinder block about the point 43 where the contact face 39 abuts control face 18a. In accordance with prior art construction, a hydrostatic pressure face is provided in the region 43 which develops a force 44 counteracting the higher pressure in the region 43 produced by the centrifugal force. In this manner, metallic contact between control faces 11a and 13a is to be prevented. However, such a force 44 tends to lift the cylinder block olf control face 11a and reduces the force at which control face 18a is pressed against control face 11a. In the construction of the present invention, the tilting moment produced by centrifugal forces on the cylinder block is also compensated, but not by urging cylinder block 18 away from control face 11a in the region 43, but by reducing the force acting on the lower part of control face 18a by making the corresponding portion of the low pressure area 48, 38 greater than the corresponding portion of the high pressure area 33.

In this manner, the pressure at which the cylinder block is pressed against the control face 11n is not reduced while nevertheless the tilting moment produced by the centrifugal force is compensated. Since the opposing force is smaller in the lower region of control face 11a than in the upper region, the pressure acting on the cylinder block can be divided into a uniform force and an additional force 46 which counteracts the tilting moment produced by the difference between the forces exerted on the upper and lower pistons by the centrifugal force. In such ian arrangement, it is also possible to provide a hydrostatic pressure field for producing a force 44, and by suitably designing the shape and position of areas 38 and 48', it is possible to balance cylinder block 18 completely so that the control faces 11a and 13a are exactly parallel at the normal rated number of revolutions;

However, since the tilting moment produced by the centrifugal forces varies with the rotary speed of the cylinder block, while the apparatus can be designed only for producing hydrostatic forces compensating a particular tilting moment, it is more desirable to make the hydrostatic balancing forces depending on the rotary speed of the apparatus, and such a solution will now be described with reference to FIG. 6. Like parts are indicated in FIG. 6 and FIGS. 1 and 5 by the same reference numerals.

The design of control face 11a may be as illustrated in FIG. 3 or FIG. 4. A central recessed area 3@ is provided with pressure fluid from ports 31 or 32 opening in a circular contact face 30. The recessed area 33 is connected by ducts 34 and 35 to a cylinder bore 48 which is closed by a threaded plug 50 having a central bore 49 to which a tubular member 53 is soldered. Tubular member 53 projects into a bore 51 in a valve piston 47 which defines with the end face of cylinder bore 48 a chamber communicating with bore 51 through a throttling conduit 52, and with the recessed annular area 40 through a duct 41.

An annular peripheral recess 56 in piston 47 forms an annular shoulder 57 with the peripheral surface 55 of valve piston 47, and communicates through transverse bores 58 with the central bore 51. The other end of valve piston 47 is spaced from plug 50 by a space 60 in which a spring 54 is mounted in a position surrounding tubular member 53 and abutting plug 5t) and valve piston 47.

During operation of the apparatus as pump or motor pressure uid leaks across contact tace into the recessed areas 33 and 40. Pressure iiuid flows from the recessed area 46 through duct 41 into cylinder bore 48, and through the throttling duct 52, which is of suicient width, into the central bore 51 and through tubular member 53 and conduit 49 to the low pressure side of the apparatus. Since the throttling conduit 52 is not particularly narrow, the hydrostatic pressure is the recessed area 40 is comparatively low.

At the same time, pressure liuid flows from recessed area 33, and ducts 34 and 35 into the annular recess 56, and out of bores 51 and 49. However, the annular edge 57 of valve piston 47 thro-ttles the flow from conduit to 55 in accordance with the position of piston 52. In one position of piston 52, duct 35 is completely closed. In the illustrated position, some fluid can flow out of conduit 35, and if piston 47 is moved to the right as viewed in FIG. 6, a greater amount of fluid can be discharged from recessed area 33 so that the pressure developed in the recessed area 33 depends on the position of the throttling valve piston 47.

If the desired normal gap filled with pressure oil is present between the control faces 11a and 18a, the flow of leakage oil into recessed area 46 is small and just sufficient for preventing contact between the metal control faces by the layer of flowing leakage oil. If the gap widens, a greater amount of leakage oil passes into recessed area 40, and Hows through throttling duct 52, which has sharp edges, and out of bores 51 and 49, as described above. Some oil also flows through a thottling duct 59 into space 66.

Since a greater amount of oil flows through the wider gap into recessed area 40, a greater pressure differential develops on opposite sides of throttling duct 52, which has sharp edges, so that the pressure on the front end of piston 47 is greater than the pressure at the rear end of the piston in space 60. Due to the pressure difference, the valve piston 47 is moved to the left as viewed in FIG. 6 against the action of spring 54, while oil contained in space 611 ows back through throttling duct 59 into annular recess 56. The control shoulder 57 of valve piston 47 moves to the left, and the peripheral surface of the valve piston further closes duct 35 producing a greater throttling action so that less or no oil can be discharged from area 33 into ducts 34 and 35 whereby the pressure in recessed area 33, and in cavity 45 increases, cavity 45 between cylinder block 18 and casing 12 communicating through space 26 with the recessed area 33, as described with reference to FIG. l.

Since a greater surface of cylinder block 1S is eX- posed to the pressure in cavity 45 than the surface of the recessed area 33, and since comparatively low pressure prevails in the recessed area 40, cylinder block 18 is pressed to the left and the width of the gap between the control faces is reduced.

The communication between the recesses 56 and space 6) through throttling duct 59 has a damping eifect on valve piston 47 since the speed at which liuid can enter and leave space is limited.

In this manner, accidental and undesired movements of valve piston 47, which may occur due to jolts on the apparatus, are prevented. This is of importance because the pressure drop along throttling duct 52 should be as small as possible so that the spring 54 is selected to oppose the piston movement with a small force only, as is necessary to produce a substantial piston movement for a very small pressure differential along throttle duct 52. Therefore, spring 54 cannot hold piston 47 in place when the apparatus and piston 47 are subjected to a shock or vibration.

Consequently, the embodimen-t of FIG. 6 is particularly suited for hydraulic apparatus in which the forces acting on 'the cylinder block vary considerably, such as is the case for pumps in which the angle of the slanted abutment surface of casing member 23 is adjustable, which results in a substantial change of the moment produced by the centrifugal forces acting on the pistons.

In the embodiment of FIG. 6, the counterbalancing force is automatically adjusted depending on the width of the gap between the control faces, and the amount of leakage oil flowing through the gap.

In the embodiment of FIG. 7, the counterbalancing force is automatically adjusted in accordance with variations of the rotary speed. Control face 11a of the apparatus shown in FIG. 7 may be constructed as described with reference to FIG. 3 or FIG. 4. As explained above, in the construction of FIG. 4 the tilting moment produced by centrifugal forces acting on differently positioned pistons is better compensated.

The recessed inner area 33 is connected with the space 26 and through the play of the toothed coupling member 17 with the cavity 45 in the casing. As explained with reference to FIG. 3, segment-shaped contact surfaces are provided on control face 11a and surrounded by recessed area 40. The circular contact face 39 seals the recessed area 46 from cavity 45. Recessed area 40 is connected with a duct 41 having a threaded end portion 37 into which a conduit, not shown, leading to the low pressure side of the apparatus is threaded. Consequently, low pressure prevails in the circular recessed area 40 over which the port of a duct 62 in cylinder block 18 passes in circumferential direction during rotation of the cylinder block. Duct 62 communicates with a recess 53 in cylinder block 18 closed by a threaded plug 64 having a central bore opening into a circumferential portion of cavity 45. An annular portion of plug 64 surrounds the central opening of the same and forms a valve seat for a movable valve member in the form of a circular disk 66 which is held on the valve seat by a spring 65. The force of spring 65 is just sutlicient for this purpose and maintains valve member 66 in the illustrated closing position in all turned positions of cylinder block 18, irrespective of shocks and vibrations.

During operation of the hydraulic apparatus in any direction of rotation, pressure fluid leaks into recessed areas 33 and 40. The pressure in area 40 is immediately relieved through conduit 41 while pressure fluid flows from area 33 through space 36 into cavity 45, as described with reference to FIG. 1, and exerts on the surface of cylinder block 18 a pressure urging the cylinder block to the left as viewed in the drawing, since the effective surface of recessed area 33 is smaller than the effective surface of cylinder block 18 located in cavity 45.

The pressure in cavity 45 builds up until it is sufficient to open valve 64, 66 by moving valve member 66 away from its valve seat so that the pressure uid in cavity 45 can flow through duct 62 into the recessed area 40, and from there out of the discharge duct 41.

If the apparatus runs at a low rotary speed, substantially only the force of spring 65 tends to maintain valve member 66 in the closing position, so that a slight pressure increase in cavity 45 will result in opening of the throttling valve 65, 66, 64 and in relief of the pressure in cavity 45, permitting an increase of the width of the gap between control faces 11a and 18a. Under such operational conditions, there is no substantial pressure difference between cavity 45 and recessed area 40.

However, if the apparatus is operated at high rotary speed which causes the development of substantial centrifugal forces acting on the pistons, and the corresponding tilting moment on cylinder block 18, a substantial centrifugal force acts also on valve member 66, urging the same to tightly close the throttling valve. Fluid under pressure in cavity 45 can only flow through throttling valve 64, 66 if its pressure is sufficiently high to overcome not only the action of spring 65, but also the centrifugal force acting on valve member 66. Since the centrifugal force acting on valve member 66 depends on the rotary speed of cylinder block 18 in accordance with a square function, the pressure in cavity 45 depends also on a square function of the rotary speed since only a correspondingly increased pressure will be suflicient to lift the valve member 66 from the valve seat. The force of the soft spring 65 may be disregarded.

As desired, the hydrostatic balancing force in cavity 45 is mainly effective at high rotary speed, so that the cylinder block is held in the desired position on control face 11a against the very high tilting moment produced on cylinder block 18 by the centrifugal forces of the differently displaced pistons, as explained with reference to FIG. 5. An advantage of the embodiment of FIG. 7 is that the discharge ow of the pressure fluid is not inhibited above a certain pressure limit.

Since the center of gravity of cylinder block 18 is displaced by the provision of the throttling valve 64, 66, 65 and duct 62, correspondi-ng ducts and masses are advantageously provided in a diametrical position on the cylinder block to balance the same during rotation.

The embodiment of FIG. 8 operates on the same principle as the embodiment of FIG. 7, but instead of the outer recessed area 40, the inner recessed area 33 is connected to the low pressure side of the pump. Recessed area 33 may be concentric with shaft 13, or eccentric, as described with reference to FIGS. 3 and 4.

In the embodiment of FIG. 8, no segment-shaped contact surfaces 38 and surrounding recessed areas are provided but a single circular and annular recessed area 69 surrounds the inner recessed area 33 spaced from the same by contact surface 30 in which the inlet and outlet ports 31 and 32 are located. A radial duct 70 connects the narrow annular recessed area 69 with the circumferential portion of cavity 45. Cavity 45 communicates through the teeth of coupling ring 17 with the right hand end of space 26 in cylinder block 18. The left part of space 26 is separated and sealed from the fluid in cavity 45 by a pair of annular flanges 76 between which a resilient O-ring 79 is mounted in an annular recess 77.

A radial bore 71 connects space 26 and recess area 33 with a valve chamber 72 closed by a threaded plug 73 which has a central bore opening in the circumferential portion of cavity 45 and forming a valve seat for a movable valve member 80. The shape of valve member 81)V is best seen in FIG. 9. Valve member has three straight sides, and three slide blocks 76 sliding on the cylindrical surface of valve chamber 72 for guiding valve member 80 during movement away from and. toward the valve seat. A spring 74 urges valve member 80 against the valve seat of plug 73 so that in the illustrated closed condition of the throttling valve 80, 73, no fluid can flow from cavity 45 into space 26 which is connected by recessed area 33 and ducts 34 and 35 to the low pressure side of the apparatus.

When the apparatus is operated as pump or motor n a-ny desired -direction of rotation, the fluid in recessed area 33 lcan flow directly to the l-ow pressure conduit of the apparatus so that low pressure prevails in space 26 and bore 71.

Pressure fluid leaking from the high pressure port into the circular annular recessed `area 69, flows through grooves 70 into cavity 45 producing a hydrostatic pressure in the same acting on the surface of cylinder block 18. The uid in cavity 45 cannot flow beyond the sealing ring 79 into space 26, but the pressure is suflicient to open valve member 80 against the action of the weak spring 74 so that at low rotary speed of cylinder block 18, valve 80 opens and fluid is discharged from cavity 45 through space 26, recessed area 33 and ducts 34 `and 35. Consequently, at low rotary speed, the hydrostatic pressure urging cylinder block 18 against control face 11a is just sucient to maintain the control faces in sliding engagement.

When the apparatus is operated at high rotary speed, a tilting moment is caused by the centrifugal forces acting on the differently displaced pistons, as explained with reference to FIG. 5. In order to prevent that a portion of the cylinder block moves away from control face 11a., a greater pressure is required in cavity 45. Such greater pressure develops automatically, since the action of the centrifugal force on valve member `80 tends to close the valve with a greater force `than at lower speeds so that the pressure in cavity 45 rises until it is suicien'tly great to overcome not only the resistance of spring 74, but also the centrifugal force acting on valve member 80. Since the centrifugal force increases in accordance with a square function of the yrotary speed, a corresponding increase of the pressure in cavity 45 is required for opening valve 73, 80 against the action of the centrifugal force. Since the tilting moment exerted by the centrifugal forces on cylinder block 18 `depends on a square function of the rotary speed, it is fully compensated by the pressure in cavi-ty 45 which increases according to the same function.

In the embodiment of FIG. 7, where the recessed area 40 communicates with the throttling valve and the discharge duct, the full pressure of cavi-ty 45 also prevails in space 26. In the embodiment of FIG. 8, where the central :recessed area 33 communicates with the discharge lduct and throttling valve through space 26, the same must be sealed from cavity 45 which is accomplished by the sealing ring 79. Evidently, an asymmetrical arrangement of the recessed inner and outer pressure areas, as described with reference to FIG. 4, can be advantageously used in the embodiment of FIGS. 7 and 8.

It will be understood that each of the elements described above, or two or `more together, may also find a useful application in other types of a rotary hydraulic apparatus differing from the types described above.

While the invention has been illustrated an-d described as embodied in an axial piston pump or motor in which the tilting moment produced by the centrifugal force is counterbalanced, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the lll standpoint of prior art, fairly constitute essential char-acteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed yas new and desired to be secured by Letters Patent is:

1. In an axial piston pump or motor, in combination, casing means having a first control face and including high pressure and low pressure conduits opening in ports on said first control face; rotary cylinder means mounted in said casing means and having a second control face in sliding contact with said first control face, Aand cylinders with ports opening on said second control face, said first and second control faces forming two separate `recessed areas, one of said recessed areas communicating with said low pressure conduit, said cylinder means having a surface forming a cavity in said casing means communicating with the other recessed area; and throttling means in one of said .means connecting said other recessed area with said low pressure conduit so that leakage fluid from said high pressure port fiowing into said recessed areas and into said cavity produces on said surface a pressure exceeding an opposing pressure acting only in the other recessed area whereby said cylinder means is pressed with said second control face against said first control face.

2. In an axial piston pump or motor, in combination, casing means having a first control face and including high pressure an-d low pressure conduits opening in ports on said first control face; rotary cylinder means mounted in said casing means and having a second control face in sliding contact with said first control face, and cylinders with ports opening on said second control face, said first and second control faces forming an inner recessed area and an outer recessed area surrounding said inner area separated from the same, one of said recessed areas communicating with said low pressure conduit, said cylinder means having a surface forming a cavity in said casing means communicating with the other `recessed area; and throttling means in one of said means connecting said other recessed area with said low pressure conduit so :that leakage fiuid from said high pressure port flowing into said recessed areas and into said cavity produces on said surface a pressure exceeding an opposing pressure acting only in the other recessed area whereby said cylinder means is pressed with said second control face against said first control face.

3. In an axial piston pump or motor, in combination, casing means having a first control face and including high pressure and low pressure conduits opening in ports on said first control face, rotary cylinder means mounted in said casing means and having a `second control face in sliding contact with said first control face, and cylinders with ports opening on said second control face, said first and second control faces forming two separate recessed areas, one of said recessed areas communicating with said low pressure conduit, said cylinder means having a surface forming a cavity in said casing means communicating with the other recessed area; and throttling means in one of said means including a normally closed valve responsive to a selected pressure to open for connecting said other recessed area with said low pressure conduit so that leakage fluid from said high pressure port flowing into said recessed areas and into said cavity produces on said surface a pressure exceeding an opposing pressure acting only in the other recessed area whereby said cylinder means is pressed with said second control face against said first control face.

4. In an axial piston pump or motor, in combination, casing means having a first control face and including high pressure and tlow pressure conduits opening in ports on said first control face; rotary cylinder means mounted in said casing means and having a second control face in sliding contact with Said first control face, and cylinders with ports opening on said second control face, said first and second contro-l faces forming two separate recessed areas, one of said recessed areas communicating with said low pressure conduit, said cylinder means having a surface forming a cavity in said casing means communicating with the other recessed area; and throttling means in said rotary cylinder means including a valve having a movable valve member responsive to the centrifugal force to exert a closing force increasing according to a square function of the rotary speed of said cylinder means, said throttling means connecting said other recessed area with said low pressure conduit so that leakage fiuid from said high pressure port flowing into said recessed areas and into said cavity produce on said surface a pressure exceeding an opposing pressure acting only in the other recessed area whereby said cylinder means is pressed with said second control face against said first control face.

5. In an axial piston pump or motor, in combination, casing means having a first control face and including high pressure and low pressure conduits opening in ports on said first control face; rotary cylinder means mounted in said casing means and having a second control face in sliding contacts with said first control face, and cylinders with ports opening on said second control face, said first and second control faces forming an inner recessed area and an outer recessed area surrounding said inner area separated fro-m the same, said outer annular recessed area communicating with said low pressure conduit, said cylinder means having a surface forming a cavity in said casing means communicating with the other recessed area; and throttling means including a duct in said casing means and connecting said inner recessed area with said low pressure conduit, and a spring-loaded check valve in said duct so that leakage fiuid from said high pressure port fiowing into said recessed areas and into said cavity produces on said surface a pressure exceeding an opposing pressure acting only in the inner recessed area whereby said cylinder means is pressed with said second control face against said rst control face,

6. In an axial piston pump or motor, in combination, casing means having a first control face and including high pressure and low pressure conduits opening in ports on said first circular control face; rotary cylinder means mounted in said casing means for rotation about an axis and having a second circular control face in sliding contact with said rst control face and cylinders with ports opening on said second control face, said first and second control faces forming two separated annular recessed areas concentric with said axis, the outer recessed area communicating with said low pressure conduit, said cylinder means having a surface forming a cavity in said casing means communicating with the recessed area and throttling means including a valve in said casing means connecting said outer recessed area with said low pressure conduit `so that leakage fiuid from said high pressure port fiowing into said recessed areas and into said cavity pro duces on said surface a pressure exceeding an opposing pressure acting only in the inner recessed area whereby said cylinder means is pressed with said second control face against said first control face.

7. In an axial piston pump or motor, in combination, casing means having a first control face and including high pressure and low pressure conduits opening in ports on said first circular control face; rotary cylinder means mounted in said casing means for rotation about an axis and having a second circular control face in sliding contact with said first control face and cylinders with ports opening on said second control face, said first and second control faces forming two separated recessed areas eccentric to said axis, one of said areas surrounding the other area and communicating with said low pressure conduit, said cylinder means having a surface forming a cavity in said casing means communicating with the recessed area; and throttling means including a valve in said casing means connecting said outer recessed area with said low pressure conduit so that leakage fiuid from said high pressure port flowing into said recessed areas and into said cavity produces on said surface a pressure exceeding an opposing pressure acting only in the inner recessed area whereby said cylinder means is pressed with said second control face against said first control face.

8. In an axial piston pump or motor, in combination, casing means having a first control face and including high pressure and low pressure conduits opening in ports on said first circular control face; rotary cylinder means mounted in said casing means for rotation about an axis and having a second circular control face in sliding contact with said first control face and cylinders with ports opening on said second control face, said first and second control faces forming two separated recessed annular areas eccentric to said axis, one of said areas surrounding the other area and communicating with said low pressure conduit, said cylinder means having a surface forming a cavity in said casing means communicating with the recessed area; and throttling means including a valve in said casing means connecting said outer recessed area with said low pressure -conduit so that leakage fluid from said high pressure port flowing into said recessed areas and into said cavity produces on said surface a pressure exceeding an opposing pressure acting only in the inner recessed area whereby said cy-linder means is pressed with said second control face against said first control face.

9. In an axial piston pump or motor, in combination, casing means having a first control face and including high pressure and low pressure conduits opening in ports on said first control face; rotary cylinder means mounted in said casing means and having a second control face in sliding contact with said first control face, and cylinders with ports opening on said second control face, said first and second control faces forming two separate recessed areas, said cylinder means having a surface forming a cavity in said casing means, said casing means having a cylinder chamber and two ducts connecting said recessed areas with said cylinder chamber, a piston in said cylinder chamber responsive to pressure in one of said areas to throttle the duct connected with the other area and having a passage for connecting the duct connected to said one area with said low pressure conduit so that leakage fluid from said high pressure port flowing into said recessed areas and into said cavity produces on said surface a pressure exceeding an opposing pressure acting only in the other recessed area whereby said cylinder means is pressed with said second control face against said first control face.

10. Apparatus as set forth in claim 9 wherein said passage extends through said piston and includes a throttling passage portion, wherein said piston has an annular circumferential recess communicating with said other area through the respective duct and two end faces forming in said cylinder chamber two rooms, one of said rooms communicating with said other area through the respective duct, said piston having another throttling duct connecting said annular recess with the other room for dampening movement of said piston, and a spring in said other room acting on said piston to oppose the pressu-re of said one area and to open the duct connected with said other area.

11. In an axial piston pump or motor, in combination, casing means having a first control face and including high pressure and low pressure conduits opening in ports on said first control face; rotary cylinder means mounted in said casing means and having a second control face in sliding contact with said first control face,`

and cylinders with ports opening on said second control face, said first and second control faces forming two separate recessed areas, one of said recessed areas communicating with said low lpressure conduit, said cylinder means having a surface forming a cavity in said casing means communicating with the other recessed area and having a duct connecting said cavity with said one recessed area; and throttling means in said duct including a valve seat and a movable valve member responsive to the centrifugal force to abut said valve seat exerting a closing force increasing with the rotary speed of said cylinder means in one of said means connecting said other -recessed area with said low pressure conduit so that leakage fluid from said high pressure port flowing into said recessed areas and into said cavity produces on said surface a pressure exceeding an opposing pressure acting only in the other recessed area whereby said cylinder means is pressed with said second control face against said first control face.

12. In an axial piston pump or motor, in combination, casing means having a first control face and including high pressure and low pressure conduits opening in ports on said first control face; rotary cylinder means mounted in said casing means and having a second control face in sliding contact with said first control face, and cylinders with ports opening on said second control face, said first and second control faces an inner recessed area and an outer recessed area, the outer recessed area communicating with said low pressure conduit, said cylinder means having a surface forming a cavity in said casing means communicating with the other -recessed area and having a duct connecting said cavity with said outer recessed area; and throttling means in `said duct including a valve seat and a movable valve member responsive to the centrifugal force to abut said. valve seat exerting a closing force increasing with the -rotary speed of said cylinder means in one of said means connecting said other recessed area with said low pressure conduit so that leakage fluid from said high pressure port flowing into said recessed areas and into said cavity produces on said surface a pressure exceeding an opposing pressure acting only in the inner recessed area whereby said cylinder means is pressed with said second control face against said first control face.

13. In an axial piston pump or motor, in combination, casing means having a first control face and including high pressure and low pressure conduits opening in ports on said first control face; rotary cylinder means mounted in said casing means and having a second control face in sliding contact with said first control face, and cylinders with ports opening on said second control fa-ce, said first and second control faces forming two separate recessed areas, one of said recessed areas communicating with said low pressure conduit, said cylinder means having a surface forming a cavity in said casing means communicating with the other recessed area, said cylinder means having a duct connecting said cavity with said one recessed area and with said low pressure conduit, said duct including a valve seat; and a throttling valve member responsive to the centrifugal force to abut said valve seat exerting a closing force increasing with the rotary speed of said -cylinder means so that leakage fluid from said high pressure port flowing into said recessed areas and f-rom said other recessed area into said cavity produces on said surface a pressure exceeding an opposing pressure acting in said other recessed area, the pressure in said cavity depending on the centrifugal force acting on said valve member and thereby on the rotary speed of said cylinder means whereby a tilting moment produced by the centrifugal force on said cylinder means is compensated.

14. An axial piston pump or -motor yas set forth in claim 13 wherein said one recessed area is surrounded by said other recessed area which is of annular configuration; wherein said cylinder means has an inner space communieating with said one recessed area, said duct opening into said inner space; and including sealing means for separating said inner space from said cavity.

1S. An axial piston pump or motor as set forth in claim 14 wherein said Cavity communicates with one end of said space, and wherein said sealing means include a sealing ring located in said space and separating said end of said space from the remaining portion of said space which communicates with said duct and with said one recessed area.

16. An aXial piston pump or motor as set forth in claim 13 wherein said duct includes a cylindrical valve chamber; a plug closing said valve chamber and having a duct forming said valve seat; and wherein said valve member is of substantially triangular shape and includes guide members slidably engaging said Valve chamber; and a spring urging said valve member against said valve seat.

17. In an axial piston pump or motor, in combination, casing means including a casing member having a first cont-rol face and high pressure and low pressure conduits opening in ports on said first control face, and a casing secured to said casing member; rotary cylinder means including a shaft mounted for rotation in said casing means, and a cylinder block secured to said shaft for rotation therewith around an axis, said cylinder block having a second control face in sliding contact with said first control face, and cylinders with ports opening on said second control face so that pressure fluid leaking between said ports flows across said first and second control faces, said rst and second control faces forming an inner annular recessed area surrounding said shaft, and an outer annular recessed area surrounding said inner area and loicated outwardly of said ports, said easing block having a duct connecting one of said recessed areas with said low pressure conduit, said cylinder block having a surface fo-rming a cavity in said casing communicating with the other recessed area; and throttling means including a throttling valve, and a -duct in one of said blocks closed and opened by said throttling valve and connecting t-he other recessed area with the low pressure conduit so that leakage fiuid from said high pres- 16 sure port flowing into said recessed areas and into said cavity produces on said surface a pressure exceeding an opposing pressure acting only in the other -recessed area until said throttling valve opens at a predetermined pressure in said cavity and said other recessed area.

18. An axial piston pump or motor as set forth in claim 17 wherein said duct is formed in said casing block and include a cylinder bore, and wherein said throttling valve includes a valve piston movable in said cylinder bore and forming in the same first and second chambers, said first chamber Icommunicating with said one recessed area, said piston having a first throttling duct 4connecting said first space with said low pressure conduit, and a peripheral recess forming a control edge controlling the width of said duct during movement of said piston, said piston having a second throttling duct connecting the second chamber with said recess for dampening movement of said piston, and a spring in said second space urging said piston to a position for increasing the flow through said duct whereby an increase of the pressure in said one recessed area causes movement of said piston to a position reducing the Width of said throttling duct.

References Cited by the Examiner UNITED STATES PATENTS 2,733,666 2/1956` Poulos 103-162 3,089,426 5/1963 Budzich 10.3--162 3,092,036 6/1963 Creighton 10B-162 MARK NEWMAN, Primary Examiner.

R. M. VARGO, Assistant Examiner.

Disclaimer 3,289,606.Paul Bosah, Ludwigsburg, Germany. AXIAL PISTON PUMP OR MOTOR ARRANGEMENT. Patent dated Dec. 6, 1966. Disclaimer led July 12, 1968, by the assignee, Robert Bosch Gmihbll. Hereby enters this disclaimer to claims 7 and 8 of smid patent.

['cz'al Gazette December 24, 1968.] 

1. IN A AXIAL PISTON PUMP OR MOTOR, IN COMBINATION, CASING MEANS HAVING A FIRST CONTROL FACE AND INCLUDING HIGH PRESSURE AND LOW PRESSURE CONDUITS OPENING IN PORTS ON SAID FIRST CONTROL FACE; ROTARY CYLINDER MEANS MOUNTED IN SAID CASING MEANS AND HAVING A SECOND CONTROL FACE IN SLIDING CONTACT WITH SAID FRIST CONTROL FACE, SAID FIRST WITH PORTS OPENING ON SAID SECOND CONTROL FACE, SAID FIRST AND SECOND CONTROL FACES FORMING TWO SEPARATE RECESSED AREAS, ONE OF SAID RECESSED AREAS COMMUNICATING WITH SAID LOW PRESSURE CONDUIT, SAID CYLINDER MEANS HAVING A SURFACE FORMING A CAVITY IN SAID CASING MEANS COMMUNICATING WITH THE OTHER RECESSED AREA; AND THROTTLING MEANS IN WITH SAID LOW PRESSURE PORT FLOWING INTO SAID RECESSED AREAS SAID HIGH PRESSURE PORT FLOWING INTO SAID RECESSED AREAS AND INTO SAID CAVITY PRODUCES ON SAID SURFACE A PRESSURE EXCEEDING AN OPPOSING PRESSURE ACTING ONLY IN THE OTHER RECESSED AREA WHEREBY SAID CYLINDER MEANS IS PRESSED WITH SAID SECOND CONTROL FACE AGAINST SAID FIRST CONTROL FACE. 